package star.servlet_2;

import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

public class checkcode_7 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //如何让浏览器5s自动刷新一次
        resp.setHeader("refresh","3");

        //在内存中创建一个图片
        BufferedImage bufferedImage = new BufferedImage(80,20,BufferedImage.TYPE_INT_RGB);

        //得到图片
        Graphics2D graphics = (Graphics2D) bufferedImage.getGraphics();
        //设置图片背景颜色
        graphics.setColor(Color.white);
        graphics.fillRect(0,0,80,20);
        //给图片写数据
        graphics.setColor(Color.BLUE);
        graphics.setFont(new Font(null,Font.BOLD,20));
        graphics.drawString(makeNum(),0,20);

        //告诉这个浏览器这个请求用图片的方式打开
        resp.setContentType("image/jpg");
        //网站存在缓存，不让浏览器缓存
        resp.setDateHeader("expires",-1);
        resp.setHeader("Cache-Control","no-cache");
        resp.setHeader("Pragma","no-cache");

        //把图片写给浏览器
        boolean write = ImageIO.write(bufferedImage,"jpg",resp.getOutputStream());

    }

    //生成随机数
    private String makeNum()
    {
        Random random = new Random();
        String num = random.nextInt(9999999)+"";
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < 7 - num.length(); i++) {
            sb.append("0");
        }
        String s = sb.toString()+num;
        return s;
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}
